However if you would Try to install ActiveSync on the Vista Machine you will getting following error:

The only option you are left with is to install the CommunicatorMobile via Cab file. Since there is no direct .cab download for CommunicatorMobile following is the workaround.

Workaround

Create a Folder name COMO on the C:\ Drive

Download .MSI in the COMO Folder.

Open Command Prompt, and Change folder to C:\Como.

Run the Following Command.msiexec /a CommunicatorMobile.msi

It will Open Following Wizard..

Choose Next Twice and Click Finish.

Go to Path (C:\COMO\COMO\BuiltIn\Microsoft Office Communicator Mobile\Setup), you will find .cab file. Now Browse the Location on you Mobile and install the CommunicatorMobile on Windows Mobile Device.While Installing you may encounter following Error. Ref Screen Shot (Installation of Communicator.Sp.cab was unsuccessful. The installation file is not intended for the device)

Reason:

From the Microsoft Web Site we can download two .MSI file for Communicator Mobile